1. Field of the Invention
This invention relates to an improved tungsten alloy and particularly to a tungsten alloy having a content of about 95 weight percent tungsten, 3 weight percent nickel, and 2 weight percent cobalt. Also described is a method of making this alloy.
2. Prior Art
The inventors believe that the alloy range and composition is both novel and has advantages over any alloys of the prior art. To the inventors' knowledge the only art concerning composition of high density tungsten alloys involves U.S. Pat. No. 2,793,951 entitled "Powder Metallurgical Process for Producing Dense Tungsten Alloys," inventors, Green et al., and U.S. Pat. No. 3,254,995 entitled "Heavy Metal Alloys," inventors, Goodfellow et al. These patents are directed to a teaching of tungsten-nickel-iron-cobalt alloys which have characteristics that are similar to the characteristics of the alloy of this invention. In particular, U.S. Pat. No. 2,793,951 discloses an alloy with a composition range containing from 80 to 96% by weight of tungsten and 4 to 20% by weight of nickel plus iron. Their preferred range of composition consists of 80 to 90% tungsten and/or molybdenum and 4 to 20% iron plus nickel in any proportions, by weight. U.S. Pat. No. 3,254,995 also discloses a high tungsten alloy, and in particular, said alloy contains between 80 to 99.9% tungsten, preferably 90 to 99.5% tungsten, with the remaining percentages being nickel and iron in equal proportions. This patent further discloses that cobalt may be used effectively in amounts up to about one percent of the total weight of the alloy, and higher amounts of cobalt may be added if desired. A still further teaching of this invention is that the iron may be partially replaced by cobalt. The nickel can also be partially replaced by cobalt.
The method of making the alloy of this invention has not been described to the inventors' knowledge in any publication or patent. The inventors wish to call the Examiner's attention, however, to the following patent which they believe represents the most closely related art: U.S. Pat. No. 3,577,227 entitled "Tungsten Materials and a Method for Providing Such Materials," inventor, Gail F. Davies. This patent discloses a method for shaping and forming metallic tungsten by coating tungsten particles with a minor amount of metallic rhenium and thereafter compacting and partially sintering said coated particles. The patent further discloses a method for providing intricate shapes of high temperature resistant, nonductile tungsten by resintering said compacted and sintered rhenium-coated tungsten particles at a temperature sufficient to diffuse the metallic rhenium into the tungsten. In particular, this method compacts and sinters the rhenium-coated tungsten particles at a temperature between 900.degree. and 1200.degree. C to diffuse the rhenium into the tungsten body, and resintering the coated tungsten body at a temperature between 1400.degree. and 2000.degree. C.